Queen Alexandra of England in mourning for Queen Victoria. She is wearing Victoria's small crown, a huge multi strand pearl necklace with tassels and down the front of the skirt, three diamond chains suspended by bow brooches. Picture is heavily retouched; Alexandra is about 58 here.
One of the interesting characteristics of Kokoshnik or fringe tiaras is that each piece is attached only to the base, so it is free to move unless fastened into a frame. That is why they are often worn as necklaces or swag corsages as well. The tiara in question would not need to be altered from the version Alexandra wore to the version we see now, if the central jewel is indeed a hairpin.